Police responded to the South Bay Medical Center on the 25000 block of Vermont Avenue shortly after 11 a.m., officials said.
After searching for the suspect, police located him in an emergency room not armed with a weapon and said there was no evidence he was armed or that a shooting occurred.
Prior to the suspect being taken into custody, the hospital was placed on lockdown as a precaution.
People at the hospital were asked to shelter in place.